1. Field of the Invention
The present invention generally relates to computer-implemented color management systems, and processes, and more particularly to selection of a technique for performing gamut mapping from a source gamut to a destination gamut, wherein the selected technique can be a combination, or hybrid, of conversion techniques.
2. Description of the Related Art
In a color management system, gamut mapping is performed to convert, or map, colors between a source gamut and a destination gamut. Each color device has a gamut, which represents the colors that are reproducible by the device. Device gamuts may differ in the sense that not all colors from one device can be reproduced by another device. If a source device's gamut is larger (i.e., contains more reproducible colors) than a destination device's gamut, gamut mapping is performed to convert colors in a source image to colors reproducible by the destination device.
Mapping color data for use with a given device, and its associated gamut, typically entails the use of a gamut mapping algorithm (GMA), which maps colors that fall outside the gamut to an in-gamut color. Gamut mapping is typically performed in a color appearance color space, which is device-independent, and which defines a color with regard to its lightness, chroma and hue aspects. In contrast, a device dependent color space defines a color in terms of its color components. For example, in an RGB device-dependent color space, a color is defined in terms of red, green and blue color components, and in a CMYK color space, a color is defined in terms of cyan, magenta, yellow and black color components.
Ideally, one GMA would be used to map any type of source color data from a source gamut to a destination gamut. However, it has been found that no one GMA works best for all color data. In fact, a number of GMAs have been developed, which have been tested for different types of color images, device gamuts and rendering intents. As a result, knowledge has been gained as to which GMAs are optimal under certain situations. However, colors in a color image can vary widely with respect to their lightness, chroma and hue aspects such that the use of a single GMA to convert all of the colors in the image can result in undesirable results, such as the appearance of artifacts (e.g., uneven transitions in an image and/or a “washing out” of saturated colors) in the output.
Thus, a conventional approach which maps between source and destination gamuts using a single conversion technique for all colors in a source image is not optimal, since it does not take into account specific aspects of each color to be mapped.